Light projector



June 23, 1931. T. P. DUNCAN.

LIGHT PROJECTOR Filed Dec. 31, 1929 gwuentov atkommq Patented June 23, 1931 UNITED STATES THOMAS P. DUNCAN, JR, NEWPORT NEWS, VIRGINIA.

LIGHT PROJECTOR Application filed December 31, 1929. Serial No. 417,756.

This invention relates to improvements in light projectors such as those commonly used upon motor vehicles, and pertains particularly to an improved incandescent bulb structure designed for use in association with the usual parabolic reflectors of such projectors The primary object of the present lnvention is to provide an incandescent light WhlC-h when placed in the usual position in a parabolic reflector of a vehicle headlight Wlll coact therewith to project in a straight beam forwardly thereof, all of the 7 light rays emitted by the bulb filament. In the present light projector a substantial portion of 16 the light rays emitted by the lncandescent bulb therein escape without comlng into contact with the surrounding reflector so that they are lost instead of being pro ected forwardly in the same manner as those rays which fall upon the reflector.

In the incandescent bulb structure embodying the present invention, the forward end of the bulb is pressed inwardly formlng an interior convex surface which is brought into close proximity to the tip of the filament in the bulb. The exterior surface of this 1npressed portion is silvered so that when the bulb is in place in a light projector, w1th the point of the filament at the focal point of the reflector, a line drawn from the filament to the periphery of the reflector will be tangential to the surface of the in-pressed portion of the bulb, and those light rays emitted by the filament within the area defined by such a line will be reflected back and dispersed over the surface of the reflector at such an angle as to be projected forwardly therefrom 1n a plane parallel with the axial center of the reflector.

40 With this type of bulb the blind spot produced at the center of the reflector Wlll be only slightly larger than that normally present in the ordinary type of reflector and the illuminatin power of the light of the projector will e greatly increased. I

The invention will be best understood from a consideration of the following detailed description taken in connection with the accompanying drawings forming a part of the present invention with the understanding,

however, that the invention is not confined to an strict conformity with the showing of the rawings but may be changed or modified so long as such changes or modifications mark no material departure from the salient features of the invention as expressed in the appended claim.

In the drawings Fi re 1 is a diagrammatic vertical longitu nal section of a light projector showmg the incandescent bulb embodying the present 1nvention in position therein, the same bemg partly in section;

F1gure2 is a perspective view of the bulb. Referring more particularly to the drawlugs, the numeral 1 indicates generally a light projector of the character normally used upon motor vehicles in which a parabolic reflector 2 is mounted, through the radial center of which an incandescent light socket 3 extends.

The light bulb devised for use in association with such a reflector is indicated'generally by the numeral 4, the base being indicated by the numeral 5, the globe by the numeral 6, and that portion of the filament which becomes incandescent when the electric current is passed therethrough being indicated by the numeral 7.

That end of the bulb or globe 6 opposite the base 5 is pressed inwardly to provide a convex inner surface 9, the radial center of whlch is upon the longitudinal center of the bulb and has the tip of the filament 7 in close proximltythereto. The outer or concave sur- 35 face of this portion 8 is suitably silvered, as indicated at 10, so that the convex inner side w1ll present a silvered surface to the filament. This silvered coating is of course, covered in the usual manner to protect it from damage, 90 such for example, as by applying a coating of black paint or any suitable substance.

The convex mirror thus formed in the forward end of the bulb 4 is preferably of parabolic contour and is so located with respect 95 to the tip of the filament 7 that when the bulb is in position in the reflector 2 with the filament at the focal center thereof, lines drawn from the tip of the filament to the outer edge or periphery of the reflector will be tangential to the reflecting surface 9. From this it will be readily seen, as illustrated in Figure 1, that light rays issuing from the filament 7 within the angle defined by the lines extending therefrom tangentially of the reflecting surface 9, will fall upon t is surface and be reflected and 5 read rearwardly over the surface of the re ector 2 from which they will be reflected forwardly along lines parallel with the axis of the reflector and with those beams projected therefrom which fall directly on the reflector from the light source.

Thus, the light rays which would normal- 1y be thrown out by the filament 7 beyond and laterally of the reflector will be interrupted and thrown back for reflection therefrom so that the light beam will be greatly intensified and the peripheral illumination of the projector cut down.

Having thus described my invention, what I claim is An incandescent lamp for use with a parabolic reflector, comprising a bulb, a filament within the bulb formed to rovide a radiant designed to be located at t e focal center of the reflector, an in-pressed portion at the forward end of the bulb havin the center in relatively close proximity to t e filament, and a silvermg substance upon the outer surface of the in-pressed portion providing a convex mirror facing the filament, said in-pressed portion being of substantially parabolic contour and so disposed relative to the radiant as to intercept all light rays issuing therefrom in an angle defined by lines drawn from iheibradiant tangential to the reflector of the In testimony whereof I hereunto aflix my signature. 7

THOMAS P. DUNCAN, JR. 

